A gunman opened fire inside a Baptist church in Sutherland Springs in the state of Texas, killing at least 27 people and injuring 20 others.

Image Source : AP Officials at the scene of a fatal shooting at the First Baptist Church in Sutherland Springs, Texas

In yet another case of mass shooting in the US, a gunman dressed in black tactical-style gear and armed with an assault rifle opened fire inside a church in a small South Texas community on Sunday, killing at least 26 people, including the pastor's 14-year-old daughter, officials said today.

The incident, which left at least 20 other people injured, occurred on Sunday at the First Baptist Church in Sutherland Springs in Wilson County where a man in "full gear" barged into the church and began shooting parishioners.

The gunman was killed in the aftermath, the local media quoted police as saying, although it is not sure if the deputies killed the shooter or he took his own life.

The shooter was identified as Devin Kelley who lived in a San Antonio suburb. A US official said Kelley doesn’t appear to be linked to organized terrorist groups, AP reported.

The official said investigators are looking at social media posts Kelley may have made in the days before Sunday’s attack, including one that appeared to show an AR-15 semiautomatic weapon.

At the news conference, Freeman Martin, the regional director of the Texas Department of Public Safety, said the attacker was dressed all in black, wearing tactical gear and a ballistic vest, when he arrived at a gas station across from the First Baptist Church at around 11:20 a.m.

He crossed the street and started firing a Ruger AR rifle at the church, and continued after entering the building. As he left, he was confronted by an armed resident who chased him. A short time later, the suspect was found dead in his vehicle at the county line, Martin said. There were several weapons inside.

Martin said it’s unclear if the attacker died of a self-inflected wound or if he was shot by the resident who confronted him. He said investigators weren’t ready to discuss a possible motive for the attack. He said the dead ranged in age from 5 to 72 years old. Twenty-three were found dead in the church, two were found outside and one died after being taken to a hospital.

Federal law enforcement swarmed the small community 30 miles southeast of San Antonio after the attack to offer assistance, including ATF investigators and members of the FBI’s evidence collection team.

Among those killed was the 14-year-old daughter of the church’s pastor, Frank Pomeroy, and his wife, Sherri. Sherri Pomeroy wrote in a text message to the AP that she and her husband were out of town in two different states when the attack occurred.

Sutherland Springs is a community of about 400 people 30 miles (48 kilometres) southeast of San Antonio.

Meanwhile, President Donald Trump tweeted expressing grief at the mass shooting incident. He said he is monitoring the situation from Japan.

"May God be with the people of Sutherland Springs, Texas. The FBI & law enforcement are on the scene. I am monitoring the situation from Japan," he tweeted.